Objective:
The Rangeland Hydrology and Erosion Model (RHEM) is a new process-based model developed by the USDA-ARS. The model has been developed for assessing the runoff, soil erosion rate, and sediment delivery rate and volume on rangelands at the hillslope scale for a rainfall event. Evaluation of RHEM performance is a key element for its acceptance as a useful tool. Therefore, the objective of the research work is to evaluate the performance of RHEM and its new components especially when it is applied to disturbed rangelands.

Approach:
In order to accomplish the objective of the research, the following tasks will be performed:
1. Evaluate the new width (w) and hydraulic friction (ft) equations for
concentrated flow in RHEM using independent plot-scale data.
2. Evaluate the current parameterization equation for splash and sheet
erodibility (Kss), and hydraulic conductivity (Ke) in RHEM on disturbed
rangeland, and if necessary develop new parameterization equations
specifically for disturbed rangeland.
3. Evaluate the RHEM concentrated flow erodibility approach (Kw(max)) and its
parameterization equations using independent data.
4. Evaluate the performance of RHEM for disturbed rangelands. The performance
of the model will be evaluated without calibration as well as by optimizing
some of the sensitive parameters such as Ke .The new probabilistic approach
for partitioning overland flow into concentrated and sheet flow as well as
parameterization of hydraulic friction (ft) for routing the overland flow
will be also tested.